Electric furnace



S. N. CASTLE.

ELECTRIC FURNACE.

APPLICATION FILED JUNE 14, 1918.

1 ,358,6 1 7, Patented Nov. 9, 1920.

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, quired for use in the furnace.

SAMUEL N. CASTLE, OF NEW ROCHELLE, NEW YORK.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Nov. 9, 1920.

Application filed June 14, 1918. Serial No. 240,104.

To all whom it may concern:

Be it known that I, SAMUEL N. CAsTLE, a citizen of the United States, residing at New Rochelle, Westchester county, and State of New York, have invented new and useful Improvements in Electric Furnaces, of which the following is a specification.

This invention relates to electric furnaces supplied with alternating currents.

The object of the invention is to improve the power factor of alternating current circuits supplying furnaces.

When electric furnaces are supplied with alternating currents, it has been found that the power factor is low. The currents supplied to the furnace are usually very large and generally transforming apparatus is supplied for transforming the comparatively high voltage and low currents of the source of supply into the large currents re- On account of the extremely large currents used in the furnace, the leads to the furnace carrying these currents provide a large number of ampere turns so that if readily permeable magnetic circuits are provided for the mag netism set up by the conductors, a very high induction will result, and this in turn will cause a decrease in the power factor. Heretofore in order to meet various mechanical and other conditions, the conductors carrying these high currents have been placed in proximity with the iron of the furnace structure for considerable distances so that the self-induction of these conductors was very greatly increased. According to the present invention, the leads carrying the heavy currents referred to, are so disposed that they are substantially free from any increase of induction by exterior magnetic material with the result that the self-induction of the leads is very greatly decreased and the power factor improved correspondingly.

Other and ancillary objects of the invention will appear hereinafter.

In the accompanying drawings which illustrate the invention- Figure 1 is a side elevation of furnace apparatus and connections embodying the invention; and

Fig. 2 is a top plan view of the same.

Referring to the drawings, the furnace comprises a crucible or a holder for the charge 1, which is pivotally mounted after 8, 9 and 10 on the electrodes.

the well known manner of such furnaces, so that it is capable of being tilted into the position as indicated by the dotted lines to permit the molten metal, etc., to be poured out at the spout 2. Suitably mounted at the side of the furnace, are masts 3, 4 and 5, to which are secured arms 5', 6 and 7 in the outer extremities of which are clamped the electrodes 8, 9 and 10, these electrodes projecting down into the furnace after the usual manner. The masts 3, 4 and 5, are slidable vertically by well known apparatus, so as to accomplish the feed of the electrodes into the furnace, as may be necessary. The manner of mounting these masts and operating them to feed the electrodes is well understood in the art.

The furnace herein shown is three-phase, although it will be understood that singlephase or any suitably poly-phase currents can beemployed. The three-phase transformer 11 has its primary side connected with any suitable source of three-phase currents, usually of high potential, so as to facilitate the transmission from the generating point to the transformer. From each of the transformer secondary terminals extend suitably insulated conducting bars 12, 13 and 14. To the ends of the bars 12, 13 and 14 are electrically connected the flexible leads 15, 16 and 17 respectively, the other ends of these leads being respectively connected to the ends of conducting bars 18, 19 and 20, which bars are respectively mounted in insulating blocks 21, 22 and 23 respectively mounted on the tops of the masts 3, 4 and 5. These blocks are of such thickness that the conducting bars 18, 19 and 20 forming part of the furnace supply leads, are raised an inch or two or even several inches above the ends of the masts, so that a magnetic gap is produced which prevents any material increase of induction by reason of the presence of the masts. It is further to be observed that simply the ends of the masts are presented to the conductor so that there is no considerable extent of magnetic material along the conductor and with the gap just spoken of. the inductive effect is reduced to a negligible amount.

To the other ends of the bars 18, 19 and 20 are secured the conducting strips 24, 25 and 26 which are connected with the clamps Connections are thus completed from the secondary terminals of the transformer 11 to the electrodes and at all points between the transformer and the electrodes the connecting leads are maintained at such a distance from any of the iron structure of the furnace or other permeable objects that the magnetic circuits of the induction about them are of substantially the reluctance of the air. In other words, the leads are not in such intimate relationship with any material of high permeability that their induction is increased above what it would be in air beyoncl a negligible amount. Of course any magnetic material no matter how remote, would theoretically have effect upon the induction about a conductor. In the apparatus shown, the closest approach of the leads to magnetic material, is at the point at which they pass over the ends of the masts 3, 4 and 5, but as has been before stated, the extent of magnetic material is not great, it is separated from the conductor by a magnetic gap and the flexible leads are held at a distance from the masts by being secured to the ends of the bars 18, 19 and 20. These flexible leads permit the tipping of the furnace as before referred to.

While the invention has been illustrated in what is considered its best application, it may have other embodiments without departing from its spirit and is not therefore, limited to the structure shown in the drawings.

What I claim is- 1. The combination with a tilting electric furnace having electrodes, of means for comprising vertical masts tilting therewith to which said electrodes are secured and said leads being supported at the upper portions of said masts.

3. The combination with an electric furnace having electrodes of means for supplying alternating current thereto comprising a transforming apparatus and leads from the said apparatus to the said electrodes, said leads comprising flexible conductors connected at one end with said transformers and at the other end with conducting bars mounted in insulators, said furnace comprising vertical masts to which the electrodes are secured, and said insulators being mounted upon the upper ends of said masts and spacing said bars therefrom, said leads further comprising conductors from said bars to said electrodes.

4. The combination with a tilting electric furnace having electrodes, of means for supplying alternating current thereto comprising a transforming apparatus and leads from said apparatus to said electrodes having a magnetic circuit of substantially the reluctance of air, the furnace structure comprising posts vertically movable with relation to the remainder of the structure and tilting with said furnace, said electrodes being secured to said posts and said leads being supported at the upper portions of said posts.

5. The combination with a tilting electric furnace having electrodes, of means for supplying alternating current thereto comprising a transforming apparatus and leads from said apparatus to said electrodes, the furnace structure comprising posts vertically movable with relation to the remainder of the structure and tilting with said furnace, said electrodes being secured to said posts and said leads being supported at the upper ends of said posts, said leads between said tranformer apparatus and said electrodes being removed from proximity from any ferric metal by a distance such that the reluctance of the magnetic circuit is substantially-that of air.

In testimony whereof I have signed this specification this 5th day of June, 1918.

SAMUEL N. CASTLE. 

